A license is an agreement that permits the use of something. In the area of intellectual property, such permission might include, for example, the copying of software, the use of a patented invention, or the distribution of products under a trademark or particular name.
Without a license, any use or exploitation of an owner's intellectual property by another would amount to illegal copying or infringement. Such copying would be improper and could be stopped through legal intervention if the intellectual property owner wanted to take such action.
Unscrupulous individuals and businesses, such as counterfeiters, often attempt to use one's intellectual property without permission. Such exploitation on the part of these individuals and businesses is often difficult to detect and to trace. Moreover, the exploitation of an owner's intellectual property might occur alongside an apparent authorized use of the property, and such exploitation can also be difficult to detect.